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Full text of "Practical Organic Chemistry"

PRACTICAL ORGANIC CHEMISTRY

PREPARATION 88.
Benzaldehyde (Bitter Almond Oil), C0H;VCO.H
Liebig, Wohler, Anna/en, 1837, 22, i ; Lauth, Grimaux, A?m-
vlen, 1867, 143, 186.
50 grms. benzyl chloride.
40     „     copper nitrate.
500   c.c.   water.
The mixture of benzyl chloride, copper nitrate and water is
heated to boiling in a round flask (i\ litre) with upright
condenser on the sand-bath for a day (8—9 hours). A slow
current of carbon dioxide is at the same time passed through
the liquid to prevent oxidation of the benzaldehyde by absorp-
tion of oxygen from the air. During the process nitrous fumes
are slowly evolved. When the reaction is complete, the contents
of the flask are extracted with ether, and the yellow oil remaining,
after distilling off the ether, is well shaken with a satu-
rated solution of sodium bisulphite1 and allowed to stand for
a time. The colourless crystalline mass which separates
out is filtered, washed with a little alcohol and ether, and then
drained on a porcelain filter. The aldehyde is regained by
adding dilute sulphuric acid in excess and distilling in steam.
The distillate is extracted with ether, dehydrated over calcium
chloride, decanted, and the ether distilled off. Yield, about 15
grams.
2CCH3CH2C1 + Cu(NO3)2 = 2C0H6COH + CuCl2 + 2HNO,.
Properties,—Colourless liquid, with a pleasant smell ; b. p.
179° ; sp. gr. ro5o4 at 15°; it quickly oxidises in the air, forming
benzoic acid.'
Reactions,—i. Leave a drop of benzaldehyde on a watch-
glass. It solidifies by becoming oxidised to benzoic acid.
2. Add 5 c.c. concentrated ammonia to I c.c. benzaldehyclej
cork up and leave two days. Crystals of hydrobenzamide,
1 The solution is prepared either by dissolving solid sodium bisulphide in water or
by passing sulphur dioxide into powdered sodium carbonate covered with a shallow
layer of water. The carbonate dissolves with effervescence, forming a heavy apple*
green liquid smelling strongly of sulphur dioxide